1. Field of The Invention
This invention generally relates to a workstation, which employs a time-sharing/multi-tasking operating system (OS) such as UNIX (incidentally, UNIX is a registered trademark of American Telephone and Telegraph Corporation) and runs what is called a multiple-window system such as X windows (incidentally, X windows is a registered trademark of Massachusetts Institute of Technology (hereunder sometimes referred to as X window system)) and can display a dynamic image such as a video image in a specified window, (hereunder sometimes referred to as a dynamic-image displaying workstation) and more particularly to a dynamic-image displaying workstation which can perform a special-effect operation such as an automatic zooming, which requires a real time processing, in real time.
2. Description of The Related Art
In recent years, what is called a multi-media computer has been developed, which uses what is called time-based media such as audio media and video dynamic-images in addition to conventional media such as characters and graphic forms, with the intention of providing computer users with a computer which is easier to operate.
Where such a multi-media computer is realized by employing a workstation which excels in interactive processing, the workstation sometimes runs a multiple-window system such as the X window system, and makes a video dynamic-image belong to (namely, contained in) and displayed in a window. Incidentally, when a video dynamic-image is made to belong to (namely, to be contained in) a window, if the window, to which the video dynamic-image belongs, is covered (or overlapped) by another window, a part or all of the video dynamic-image, which is contained in the overlapped part of the former window, is also covered by the latter window. Further, if the window, to which the video dynamic-image belongs, is moved, the video dynamic-image is similarly moved in such a manner not to change the position thereof in the moved window. Namely, the same processing is performed on a window and a video dynamic-image contained therein.
Referring to FIG. 9, there is illustrated the configuration of such a conventional dynamic-image displaying workstation.
A central processing unit (CPU) 12 of the conventional workstation runs (namely, executes) UNIX, which is a time-sharing/multi-tasking OS, and the X window system, which is what is called a multiple-window system. Further, the CPU 12 receives data from and sends data to a main memory and input/output (I/O) devices such as a hard disk through a data bus 14. Dual port memories 1, 2 and 34 are conventional graphic frame memories, each of which usually consists of a video random-access-memory (VRAM). Further, data can be read from and written to a first port (namely, a left port as viewed in this figure) of each of the memories 1, 2 and 34. Furthermore, data can be read from a second port (namely, a right port as viewed in this figure) of each of the memories 1, 2 and 34. The number of pixels displayed horizontally and vertically on a display device of the workstation (namely, the resolution of the display device thereof) are 1280 and 1024, respectively. The memories (hereunder sometimes referred to as the buffers) 1, 2 and 34 store 24-bit data, 8-bit data and 1-bit data corresponding to each pixel, respectively. Analog data represented by video signals (more particularly, National Television System Committee (NTSC) composite video signals in this case) inputted from an external device are converted by a video-signal processing circuit 9 into digital data. Then, a predetermined processing is further performed therein and data corresponding to one field of a video image is outputted therefrom every (1/60) seconds. The CPU 12 sets control commands describing tile contents of the information on various processing to be performed on video signals. The contents of the information are, for example, positions on the screen of an external display device, which define an original picture including a video dynamic-image to be inputted to the workstation, the size of the input image, scaling parameters or factor, positions on the screen of a display device of the workstation, which define the video dynamic-image, the size of the video dynamic-image and contrast/luminance control parameters. The video signal processing circuit 9 writes data representing the video dynamic-image to the dual port memory 1 from the first port thereof and controls the data. The workstation has what is called a key plane of the memory 34 which serves to control whether or not the video image represented by the buffer or memory 1 is displayed on the screen of a color display device 8 and whether or not each pixel of graphic forms and characters represented by data stored in the buffer or memory 2 is displayed thereon. In case of this conventional workstation, a value of 1 is stored correspondingly to each pixel of the video dynamic-image at a corresponding location of the memory 34. In contrast, a value of 0 is stored correspondingly to each pixel of the graphic forms and characters at a corresponding location thereof. Further, the workstation translates 8-bit output data read from the memory 2, which indicates one of 256 kinds of colors, into 24-bit color data by using a color lookup table (or a color map) 6. A data selector 5 is practically a multiplexer 50 which selects color data originated from the memory 2 if input data S is 0 and selects color data originated from the memory 1 if input data S is 1. A signal representing output data of the data selector 5 is converted by a digital-to-analog (D/A) converter 7 into an analog red-green-blue (RGB) video signal, from which a color image is then displayed on the screen of a color display 8. If an image-data reading control signal and an image-data reading address signal, which are synchronized with the video signal sent to the color display 8, are supplied to the D/A converter 7 and the memories, respectively, as illustrated in FIG. 9, a video dynamic-image (in this case, a dynamic image of jet planes) can be displayed in a window of the multiple-window, to which the dynamic image belongs, on the screen of the color display 8 of this figure. At that time, the CPU 12 should write data representing the form of the part of the dynamic image, which is not covered by another window, to the key plane 34 quickly responding to a user's manipulation of a window. FIG. 9 illustrates a state in which the window containing the video dynamic-image is covered or screened by a pull-down menu window (hereunder sometimes referred to simply as a pull-down menu) which has a long length-ways rectangle. The pull-down menu is created and destroyed by manipulating a mouse of the workstation. Next, when the mouse is manipulated to destroy the pull-down menu in the state of FIG. 9, an event interruption is caused and delivered to the CPU 12. Then, the CPU 12 runs a window-manager program or application of the X window system so as to cause a sequence of operations of deleting data representing the pull-down menu form, which is stored in the memory 2, and filling up a rectangular empty space in the pattern stored in the memory 34. In case of relatively slow operations of, for instance, moving, resizing, creating or destroying a window in response to a user's manual manipulation of the mouse, the time-sharing/multi-tasking OS can barely follow such operations in real time.
However, in case of the application of multi-media, special-effect functions such as an automatic zooming (namely, the function of performing automatic repetitions of zooming-in on/zooming-out from a part of a scene) and a spinning function (namely, the function of performing rotations of a part of a scene around a vertical axis and around a horizontal axis) are greatly demanded in addition to the function of displaying a video image of a fixed-shape like an ordinary television set in order to make an extremely effective impression on a viewer. Further, it is necessary for achieving such special effects to change the contents of the key plane 34 in real time. Inconveniently, in case of employing the time-sharing/multi-tasking OS for processing many tasks concurrently, the CPU 12 cannot be dedicated to the rewriting of the contents of the key plane 34. Thus, if the number of tasks to be performed increases, for example, the automatic zooming cannot be effected smoothly. Unfavorably, the automatic zooming becomes performed discontinuously.
The present invention is created to resolve such a problem of the conventional dynamic-image displaying workstation.
It is, accordingly, an object of the present invention to provide a dynamic-image displaying workstation which operates under the control of a non-real-time OS and can display a video dynamic-image by using multiple windows and perform real-time special-effect functions.